1. Field of the Invention
The invention generally relates to fluid treatment tank distributor plates and, more particularly, to a distributor plate including a number of valve plates configured to selectively permit relatively unobstructed fluid flow through the distributor plate during downflow operation of the fluid treatment device and to restrict or prohibit flow through portions of the distributor plate during upflow operation.
2. Discussion of the Related Art
Water softeners are widely used for removing calcium and other deposit causing materials from so-called “hard-water.” The typical water softener relies on an ion exchanges process taking place in an ion-exchange resin bed stored in a resin tank or pressure vessel of the water softener. As the water to be processed passes through the resin-filled tank, ions of calcium and other minerals in the water are exchanged with ions found in the resin, e.g., sodium, thereby removing objectionable ions from the water and exchanging them for less objectionable ions from the resin.
In addition to having dissolved ionic contaminants that are removed by water softeners, untreated water also often contains particulate matter which must be mechanically filtered. Sometimes ion exchange resin performs the dual functions of exchanging ions and mechanical filtering. Sometimes specific filter beds are used with no ion exchange properties. These dual-function ion exchange beds and pure filter beds require aggressive mechanical scrubbing to remove the accumulated participates.
The capacity of the resin to exchange ions is finite and is reduced during the ion exchange process. If measures are not taken to regenerate the resin by replacing the undesirable ions with desirable ions, the ion exchange capacity of the resin will become exhausted. Water softeners are typically configured to periodically regenerate the ion exchange resin stored in the resin tank. Regeneration typically involves chemically replacing the objectionable ions such as calcium ions from the resin with less objectionable ions such as sodium ions. The replacement is usually performed by introducing a regenerant solution of sodium chloride or potassium chloride into the resin bed from a brine tank and thereafter flushing the regenerant solution from the bed. Regeneration of a water softener resin bed is sometimes accomplished in a direction that is co-current with the flow of water to be treated (often referred to as “downflow regeneration” or “service flow”) and is sometimes accomplished in a direction countercurrent to the flow of the water being treated (often referred to as “upflow regeneration” or “backwash flow”). The resin bed is typically backwashed in order to remove trapped particulate matter, and the resin tank can be rinsed to remove objectionable soluble materials. In order to prevent interruption of service, most water softeners are configured to allow bypass of untreated water directly to the service lines during backwash, rinse, and regeneration.
Resin tanks typically include a distributor plate (also known as a diffuser plate) positioned within the tank and supporting the resin bed. The typical distributor plate is slotted to allow bidirectional flow therethrough. However, most water softener system distributor plates are configured to favor service flow or downflow. This results in a system in which the backwash flow or upflow is relatively inefficient because the bed is evenly fluidized, and only very minimal scrubbing takes places.
Measures have been proposed to enhance scrubbing during backwash. The most widely known is the Autotrol/Osmonics/GE/Pentair turbulator. The turbulator includes a check valve in the normal riser tube/distributor combination of a resin tank that diverts backwash water through a duck bill check valve and up a tube mounted parallel to the main riser tube. This secondary tube is open at the bottom end, which is positioned about 0.5 inches above the top of the duck bill check valve. At the top of the secondary tube is another check valve which prevents water from flowing back down the secondary tube. This additional check valve is positioned slightly below the top of the ion exchange resin or other media in the tank.
In operation, backwash water is diverted through the duck bill check, jetting up the secondary tube and carrying resin with it. This resin plumes out of the cage surrounding an additional third check valve and settles back down through the bed to repeat the cycle. The motion cleans the resin better than the gentle floating action of a normal backwash.
Turbulators work reasonably well but cannot be used with an abrasive filter media. They also cannot be used with a bed having gravel under the resin or “gravel under-beds.” Because a gravel under-bed cannot be used, a portion of the ion exchange media must act as an under-bed and is not available for ion exchange. The efficiency of the water softener is reduced by the percentage of unused resin. In addition, the duck bill check valve is in the resin and is prone to plugging with resin and allowing resin migration into the plumbing lines. It is also subject to attack by chlorine and chloramines, and resin will enter the plumbing lines if it fails. Moreover, the check valve at the top of the secondary tube is prone to plugging with resin, causing a bypass path around the resin bed. This bypass results in premature discharge of hard water.
Another method of improving scrubbing during backwash flow has been to employ a distributor plate including a number of angled slots. The angled slots are configured to attempt to impart a spinning action to the upflowing water to thereby increase the scrubbing during backwash. However, such systems are generally ineffective because the flow velocity of fluids exiting the slots in the plate is relatively low such that very little, if any, spinning can be developed at typical backwash flow rates.
At least some of these issues are not unique to resin tanks of water conditioning systems but, instead, are of a concern in a variety of fluid treatment systems in which a treatment medium is subject to backwash.
The need therefore exists to provide a distributor plate arrangement that is capable of evenly distributing flow during service flow or downflow through a fluid treatment tank and that is also capable of introducing areas of higher flow during backwash or upflow to improve the scrubbing and cleaning of the treatment medium.